1. Field of Invention
The invention relates to a hybrid vehicle drive control device, a hybrid vehicle drive control method and a program thereof.
2. Description of Related Art
Conventionally, there exists various types of hybrid vehicles. For example, in a first type of hybrid vehicle, an engine and a drive motor are directly connected, so that an engine torque and a drive motor torque can be transmitted to a drive wheel. Thus, when torque that is required to make a hybrid vehicle run (vehicle requirement torque) is small, the engine is driven at the most efficient operation point on an optimal fuel consumption curve. The drive motor torque that corresponds to the amount of the engine torque in excess of the vehicle requirement torque is also absorbed as regenerative torque, and electrical energy is generated by the drive motor, which is used for charging a battery. (See Japanese Patent Laid-Open Publication No. 11-82258).
Furthermore, a second type of hybrid vehicle has a planetary gear unit that is provided with a sun gear, a ring gear and a carrier. The carrier and the engine are connected, the ring gear and a drive wheel are connected, and the sun gear and a generator are connected, wherein a portion of the engine torque is transmitted to the generator, and the remaining amount is transmitted along with the drive motor torque to the drive wheel.
In this case, in an overdrive state that reduces the engine torque in the engine and increases a speed of revolution of the engine, (the engine speed) electrical energy is generated by absorbing as regenerative torque the drive motor torque that corresponds to a portion of the engine torque transmitted from the engine to the drive motor, and the generator is driven as an electric motor using this electrical energy. (See Japanese Patent Laid-Open Publication No. 10-325344). Further, in one known example of the second type of hybrid vehicle, the hybrid vehicle, when running an engine to generate power by a generator, is moved backward by causing a drive motor to generate drive motor torque in a reverse direction such that it is sufficient to overpower the engine output (refer to U.S. Pat. No. 6,005,297).